Hydrocarbon conversion



Patented Oct. 23, 1945 UNITEDSTATE s PATENT Noi-"rflcla:

t HYDBJOCARBON CONVERSION Charles L. Thomas, Chicago, Ill., assigner to Unifl versal Oil Products Company, Chicago, Ill.,a`` corporation of Delaware Application June 30, 1941, Serial No. 400,373 i 4 Claims. (Cl. IBG-52) The present invention relates to the conversion o1' petroleum oils and deals more specifically with improvements in cracking such oils in the presence ofsolid catalysts.

. This` invention is concerned principally with 5 the" of` process which comprises passing oil vapors over a fixed bed of catalyst in a reaction zone at the` desired processing conditions and periodically interrupting the fiow of hydrocarbons to regenerate the` catalyst. In this type of n. operation it is important to control the conversion` per-pass to` obtain the optimum yield of gasoline from the charging stock. This conver- Sion per `pass will be defined as the Weight per centof charging stock converted to gasoline .and

gas during the passage of the oil through the reaction zone. Theamount of conversion of a particular hydrocarbon oil realized in a catalytic `crackingreaction is dependent upon the catalyst activity, the space velocity of the hydrocarii bon oil` overthecatalyst,` and the temperature and pressure at which the reaction is occurring.

`By varying any one or ,more of these `factors the conversion per pass can be changed. The

conversion per pass attended by any set method of operation-will aifect the economic feasibility of the process. For instance, if too high a con'- version `pei` `pass were attained, large amountsk `of undesirable coke andlight gases would be excessively high, thereby greatly decreasing the catalyst activity. i

It can readily beseen that dur-ing the initial y maintained substantially constant `througl'iout.

the entire processing period, thereby considerably :decreasing the percentage of charging stock being converted to coke and gas during the rst portion of the period and the amounts of unconverted `materials which are to be recycled back to the process.

It has been pointed out that the fac'- tors `influencing the conversion per pass` of a particular hydrocarbon oil are the processing temperature, space velocity and catalyst activity. It has also been pointed out that the catalyst `activity decreases as the processing period length increases. Therefore, the present invention pro- ,vides methods of varying the processing -temperatures and space velocity to compensate for the formed, tending to decrease the overall gasoline production. On the other hand, if too low a conversion per'pass is maintained, the yield of desirable product formed during the processing ,period is ltoolow, necessitating the reheating and recycling fof. excessive amounts of unconverted material which will considerably increase the expenditures necessary `to carry out the cracking process. Therefore, it is necessary to determine the optimum conversion per pass desired which will give the maximum yield of desirable products Without excessive coke deposition and gas formation and which will not entail the reheating and recirculating of large amounts of unconverted materials. It `must be understood that'this `optimum yield will vary with different types of charging stocks and catalyst used but will usually `be of the order, of 25 to `50% 3 It has been found when charging a hydrocarbon `oilover a fresh or reactivated bed of catalyst in a` cyclic operation that the conversion in therst `portion of .the periodis veryhigh and tapers oit' Aas the processing period length increases. It has also been found that the carbon deposition durinitial period `of high `catalyst activity is `loss in activity of the catalyst during the processing period, thereby maintaining a substan- -tially constant conversion per pass throughout the entire processing period.

. `In .one specific embodiment the present invention comprises a process for the `catalytic conversion of hydrocarbon oil, contacting said hydrocarbon oil with a cracking' catalyst under processing conditions which Willvary'simultaneously and dependentlyto compensate for the loss of catalyst activity due to theviculing of the catalyst by the deposition of carbonaceous material upon said catalyst, thereby effecting a substantially constant conversion pei pass during the processing period.

Figs. l, 2., and 3 of the accompanying drawing diagrammatically Aillustrate three separate arrangements of apparatus in which the methods and objects `of this invention `can be accomplishedubut do not necessarily limit the invention to the use of such methods or apparatus.

Referring to Fig. l, charging oil, for example,

a Pennsylvania gas oil, is introduced from line `.I .into pump 2 which dischargesthrough valve 3 into heating coil 4 in furnace 5 where it is raised `to a temperature within the range of 850 to 1l00 F. The heated oil leaves the furnace through opened to decrease the amount ofwoil flowing to reactor II. This decrease in now is regulated to increase the time of contact between the hydrocarbon oil and the catalyst, thereby compensating for the reduction in catalyst activity and enabling the maintenance of a substantially constant conversion per pass throughout the entire processing period. The oil being diverted from' the reactor may be used for heat exchange or any other suitable application. The reactants leaving reactor II pass through-line I2 containing valve I3 to the usual fractionating and stabilizing equipment. The unconverted materiallseparated from the gasoline boiling range and lighter hydrocarbons may be recirculated back to the process. Y, e

Referring to Fig. 2, the charging stock (stream A) is introduced through line I4 to pump I5 vwhich discharges through valve I6 into heating coil I'I in furnace I8 where it is heated to a temperature between 500 and 800 F. The same charging stock (stream B) is introduced into line 2| to pump 22 which discharges through valve 23 into heating coil 24 in furnace 25 where it is raised to a temperature within the range of 850 to 1100 F. Stream A leaves heating coil I1 through .line I9 containing valvev 20 and cornbines with stream B, passing through line 2B containing valve 2'I. The two streams are combined in such proportions as to produce lthe desired temperature and space velocity in the reaction zone which will enable producing an optimum yield of gasoline without converting a large percentage .of the charging stock to coke and gas. 'I'he combined streams pass through line 30 containing valve 3'I into reactor 32. As the processing period continues the catalyst activity decreases due to fouling of the catalyst surfaces by carbonaceous materials. In order to compensate for this loss in catalyst activity, part of stream A is continuously being diverted from the ow to the reactors. The diverted portions pass through line 28 containing valve 29 and may be used in a heat exchange system or may be sent to an insulated storage vessel so that the variable use of stream A will. not introduce any heating problems. The elimination of part of the colder stream decreases the'amount of oil being passed to the reactor and increases the temperature of said oil. lThe eiect of the ydecreased space velocity and increased processing temperature can be regulated to maintain a constant vconversion per pass throughout the entire processing period. The ,reactants leaving reactor 32 through line 33 containing Valve 34 are sent to the usual fractionating and stabilizing systems.

The unconverted or partiallyv converted hydro-V reactants may be alternately switched from one reactor to the other, and in such case the catalyst in the reactor not in use is subjected to regeneration in the conventional manner.

In Fig. 3 the method is shown in which the objects of the invention can be accomplished using a multiple reactor system. To further illustrate the invention, let it be assumedthat the process is operated on the cyclic operations of the following table: It must be understood that the 'fcycle presented herein to be used as an illustration does not place undue limitation on the process, since many variations of the presented cycle can be used which will fall under the broad scope of-this invention. The letter R is used to distinguish the catalyst containers being reactivated and the letters A and B to the charge streams. A complete cycle is considered to be 360.

Reactor No.

Time of cycle:

c-9o A+1/5B VR R.

l/QB R n+1/5B. R x4-ts-. ma.

ygB R.

Referring tothe drawing, the charging. stock is introduced in two separate streams to heating coils 38 and 44. Stream Arenters through line 35 into pump 36 which discharges through valve 3'I into heating coil 38 in furnace 39 where it is heated to a temperature within the range of 500 to 800 F. and leaves the heating coil through line 40. Stream B enters through line 4| into pump 42 which discharges through valve 43into heating coil 44 in furnace 45 where it is heated to a temperature within the range of 850 to 1100 F. and leaves the heating coil through line 46.

According to the cycle of the foregoing table, reactor 55 has just been put on stream and reactor 56 has been processing for some time. Since the catalyst in reactor 55 has just been freshly regenerated, it is in a highly active state. :To avoid a high conversion per pass and the conversion of a large 'percentage of the charging stock to coke and gas, a larger volumeof hydrocarbon vapors at a lower temperature isY passed .will be passed through the reactor at a lower rate and a higher temperature, compensating for the loss in catalyst activity and maintaining a substantially constant conversionA per pass. VReactors 5'I and 58 are in the process of being regenerated. "Regeneration in reactor 51 has just been started, while the regeneration in reactor 58 is nearing completion. The cycle is continued in accordance with the illustrative example presented with the hydrocarbon oil passing through lines 40 and 46being introducedto any one 'or more of ,reactors v55 and 58, inclusive, through valves 4'I to 54, inclusive. 'v j It will be noted that the above arrangement "activity daring .the processing period. In the drawlugliierein attached no `regenerating equip- `ment has been included; lEIT-he regeneration may becarried lout in the usual manner. The reactors maybe manifolded so that the regenerating gases Imaybe introduced to any one orV more of the A short purge period with steam or substantially oxygenliree gases will be1 used to remove the hydrocarbon vapors before burning off l oxygen or oxygen-containing gases. A i reactors illustrated in Figs. 1, 2, and 3 may the carbonaceous materials from the catalyst with comprise," for example, a conversion zone cf the heat exchanger type wherein the catalyst is con# tained in a plurality of elongated tubular elements fili) virgin stocks having different boiling ranges. .One stream may be made up in part or entirely of the recycle from the catalytic cracking re action or it may be made up entirely or lnpart of a thermally cracked gas oil. The process as disclosed is also particularly adaptable to using stockshaving different susceptibilities to catalytic cracking and/or different carbon forming tendencies. These oils may be used as indicated above by charging one oil and then the other, charging the vmost reactive or worst carbon forming oil only in the last half of the processing period.

4The method illustrated in Fig. 1 can also be .applied to Fig. 3. The oil may be heated to the of relatively small diameter, provisionsbeing made Y "lorl passing sume suitable heat convective iiuid such` as corr-lbustiori gases in indirect heat exchange `'relationslfiip with said tubular elements to supply heatto the reactants during conversion and to cool the catalystand regenerating gases during regeneration. These reactors, on jthe other hand," may comprise cylindrical vessels contain;- ing one or o, pluralityof beds of catalytic material,

` saiovesseis oemgmsuiated to reduce radiation losses therefrom "so that the conversion reaction may be accomplished substantially adiabatically. "catalysts whichhave `been found to be effective the cracking of hydrocarbon vapors may com- The conversion products leave the reactors in Fig. 3 through lines 55 to 62, inclusive, containing valves 63 to 66, inclusive, depending upon which" reactors are being processed, passing `through the manifold line 61 into fractionator 68. "I'he cracked products are fractionated within tower SII and the insui'lciently converted materials withdrawnthrough line 1l containing valve 112;;` The unconverted materials may be `recycled back to the process, thermally cracked-or *sont to storage; The gasoline and gas "withdrawn through llneBB .containing valve TB are passed `through the `usuali condensing and stabilizing" equipment and the desired products sent to storage.` I

Although inthe previous examples the charg ingstocks used were of` the saine type of oil, it doesnot follow that this is necessary in the present invention. There are a number of variations which are within the scope of this invention.

The individual streams of oil may be virgin stock having the same boiling range or may consist of desired temperature and split `into two streams as in Fig. l. The decrease in catalyst activity can be lcompensated by the decreased volume vof oil Ilowing to the reactors. It also follows that the invention is not limited to the number of reactors which can be used in the system.

Example lI #space velocity ywas varied accordingly thereby,

maintaining a constant conversion 'of `27.7% by weight' of the charge throughout the processing period. The `yields were 21.6% gasoline, 6.1% gas and 0.45% fcarbon.

When operating under the saine temperature, `lout'at a constant space velocity of 2.4, thereby obtaining the same `average conversion, the gasoline yield was 20.8%, gas 6.9% 'and carbon 0.60%.

When comparing the above data, uit is evident that the operation in which the Space velocity was varied to maintain a constant conversion has -denite advantages over the `stamard process. Not only `is the gasoline yield 3.8% greater but the carbon deposition is about 25% less'.

This decrease in carbon deposition is very important, since 'it considerably simpliiesthe regeneration'of the catalyst.

Example II A 32 A. P. I. gravity Mid-Continent paraflin distillate' was catalytically cracked by passing the heated vapors over a catalyst comprising alumina, silica, and `zirconia at a constant space velocity of 2. The temperature was maintained at 955i F'. throughout the processing period. The conversion was 33.4% by weight of the original charge. The yields were gasoline 22.9%, recycle stock 64.4%, gas 10.8% and coke 1.9%.

j `The same charging stock was passed over the same 'type of catalyst at a constant space velocity with the temperature `being varied ata predetermined rate from S75-970 F. to main:- tain a constant conversion of 33,4%. The distribution of products was much better in the second test, the yields being gasoline 24,0%, gas 9.6%, recycle stock V64.6% and coke `.'lhe gasoline to gas relationship was improved considerably in the second test while thecarbon deposition was slightly lower.

The novelty and utility of the present invention have been shown by the preceding speciiication and examples, although neither section is intended to unduly limit its generally broad scope.

action is conducted simultaneously in at least l two of said reaction zones and the time of introduction of the hydrocarbon reactants is so regulated that said reaction zones are in diierent stages of processing, the improvement which comprises, heating separate streams of the hydrocarbon reactants each to a diierent temperature, supplying to the reaction zones as the conversion reaction progresses therein Varying portions of said separately heated streams, said portions being regulated to maintain a high space velocity and relatively low temperature in the reaction zone wherein the catalyst activity is relatively high, and to maintain .a lower space velocity and high temperature in the reaction zone wherein the catalyst a-ctivity is relatively low.l

2. In the process of catalytically cracking hydrocarbons wherein the hydrocarbon reactants are heated to reaction temperature and passed in contact with an active catalyst capable of promoting the reaction, the activity of said catalyst decreasing as the processing period progresses, the catalyst being periodically regenerated to restore its activity, and the operationbeing made continuous by employing a, plurality of reaction zones in which the catalyst is disposed, each of said reaction zones being alternately processed and regenerated and wherein the conversion reaction is conducted simultaneously in at least two of said reaction zones and the time of introduction of4 the hydrocarbon reactants is so regulated that saidreaction Zones are in diierent stages of processing, the improvement which comprises, heating separate streams of the hydrocarbon reactants each to a different temperature, supplying to the reaction zones as the conversion reaction progresses th'erein Varying portions of said separately heated streams, said portions being regulated to maintain a high space velocity and relatively low temperature in the reaction zone wherein the catalyst activity is relatively high and'to maintain a lower space ve-` locity and high temperature inthe reaction zone wherein the catalyst activity is relatively low.

3. In a process of catalytically converting h'ydrocarbons wherein the hydrocarbon reactants are heated to reaction temperature 'and passed in contact with an active catalyst capable of proaction is ,conducted .simultaneously in at mast 4two of said reaction zones and the time of introduction of the hydrocarbon reactants is so regulated that said reaction zones are in different stages of processing, the method which comprises continuously supplying to th'e `process a first hydrocarbon reactant stream of relatively .high temperature and a second hydrocarbon reactant stream of lower temperature, introducing said second stream and a portion of said rst stream into one of said reaction zones containing cata.- lyst of relatively high activity, simultaneously introducing the remainder of said first stream to another of the reaction zones containing catalyst ofv lower activity than said one reaction zone, the amount of -said'remainder being such as to maintain in said other zone a ratio of conversion products to reactants per pass substantially equal to that in said one zone, continuingv the introduction of reactants tosaid Zones as aforesaid until the activity of the catalyst therein has decreased substantially and thereafter diverting said second stream and said portion of the first stream from said one zone into a third reaction zone containing freshly regenerated catalyst while diverting said remainder of the first stream from said other zone into said one zone.

4. In the processfof catalytically converting hydrocarbons wherein the hydrocarbon reactants are heated to Areaction temperature and passed in Contact with an active catalyst capable of promoting the` reaction, the activity of said catalyst decreasing as the processing period'progresses, the catalyst being periodically regenerated to restore its activity, and the operationbeing made continuous by employing a plurality of reaction zones -in which the catalyst is disposed, each of said reaction zones being alternately processed and regenerated and wherein the conversion Vreaction is conducted simultaneously inat least two of said reaction zones and th'e time of introduction of the hydrocarbon reactants is so regulated that said reaction-zones are in different stagesV of processing, the method which comprises continuously supplying to the process a rst hydrocarbon reactant stream of relatively high temperature and a second hydrocarbon reactant stream of lower temperature, introducing said secondstream and a portion of said rst stream into one of said reaction zones containing catalyst of relatively high` activity, simultaneously introducing another portion of said rst stream to another of the reaction zones containing catalyst of lower activity than said one reaction zone, the amount of said otherportion being such as to maintain in said otherv zone a ratio of conversion products to reactants per pass substantially equal to that in said one zone, continuing the Vintroduction of reactants to said zones as aforesaid until the activity of the catalyst therein has decreased substantially, and

thereafter diverting saidsecond stream from said one zone into a third reaction zone containing freshly regenerated catalyst while diverting said other portion of the rst stream from said other zone .into said third zone and continuing the introduction of the first-mentioned portion of th rst stream into said one zone. Y y Y CHARLES L, THOMAS. 

